1. Field of the Invention
The present invention relates in general to the field of non-welding joinder techniques, such as brazing and soldering. More particularly, the present invention relates to a system and method of joining metals using non-silver or low-silver filler metals. Specifically, a preferred embodiment of the present invention relates to a system and method of brazing using copper based filler metals such as the alloys CDA 464, CDA 680, and CDA 681.
2. Discussion of the Related Art
As is known to those skilled in the art, brazing is a joining process whereby a filler metal is heated to a melting temperature which is lower than the melting temperature of the base metal and distributed between two or more close-fitting parts. The molten filler metal and flux interacts with the base metal and then cools to form a strong, sealed joint. A wide variety of filler metals and alloys may be used.
The use of copper based filler metals from the bronze family of filler metals is particularly well known in the art. Prior forms of bronze brazing, however, have required the use of high temperature fluxes. These high temperature fluxes leave behind a residue that is very difficult to remove. Removal is typically only accomplished by mechanical means such as wire brushing, chipping, or sandblasting. Furthermore, high temperature fluxes tend to form a heavy oxide layer on the base metal that leaves behind a charred or burned appearance that results in an unacceptable surface for coatings, such as painting or plating, and/or an otherwise aesthetic displeasing appearance.
Brazing with silver based filler metals has commonly been used as an alternative to bronze brazing because silver brazing does not suffer from the disadvantages that prior forms of bronze brazing have, such as, for example, the left behind residue and oxide layer formation on the base metal which is heavy, aesthetically displeasing, and difficult to remove. Brazing with silver based filler metal, however, is disadvantageous in that the silver alloys used are quite expensive.
Brazing with copper based and nickel based filler metals, in a controlled atmosphere furnace, is another form of brazing that is commonly used. Brazing with copper and nickel in a controlled atmosphere furnace is typically a batch process requiring large inventories of component pieces and filler metals. The furnaces typically need to run constantly in order to maintain a functional brazing atmosphere, which results in high utility costs and large component piece inventories. Further, large capital equipment expenditures are required to purchase and install and maintain a controlled atmosphere brazing furnace. Needless to say, it is desirable to provide a brazing method that uses less expensive filler metals than silver based filler metals, provides easier clean-up afterwards than traditional bronze brazing, and does not require the large capital and utility expenditures of controlled atmosphere furnace brazing.